托福閱讀水平的提升是一個循序漸進的過程，除了在備考過程中把握好TPO真題資料做好各類題型針對性練習與文章精讀，我們還需要盡可能多的進行拓展閱讀，提升對英文材料的熟練度和敏感度。拓展閱讀材料一般應當選擇難度與托福接近的內容，題材最好也能與常考高頻話題相關。生物學是托福閱讀常考話題之一，下面的這篇介紹蛋白質的雙語素材難度適中，大家可以拿來作為很好的托福閱讀輔助練習材料。

Protein-rich diets

Feed as well as food

As demand for protein grows, what people eat matters. So does what gets fed to animals

富含蛋白質的食譜

飼料與食物

隨著人們對蛋白質需求的增長，吃什么變得很重要。給動物喂什么也同樣重要

BETWEEN now and 2050 the planet’s population is expected to rise by a third, from 7.6bn to 9.8bn. Those extra mouths will need feeding(句型), and not just with staples(詞匯). As people grow richer, their demand for protein rises, particularly for meat and fish. Beef consumption in Asia, for example, is expected to jump by 44% over the next decade alone. 從現在到2050年，全球人口預計將增長三分之一，從76億增至98億。這些新增人口需要養活，且不能光靠主糧。隨著人們越來越富裕，蛋白質尤其是肉類和魚類的需求上升。例如，僅在未來十年，亞洲的牛肉消費量預計就將增長44%。

Raising animals to be eaten already has huge effects on the world’s environment. The number of farm animals soared during the 20th century. More than 20bn chickens, 1.5bn cattle and 1bn sheep are alive today. A quarter of the world’s land is used for grazing them. They consume 30% of the world’s crops. They guzzle(句型)water—you need about 15,000 litres of the stuff to produce a kilo of beef, compared with only 1,500 litres for a kilo of maizeor wheat. And their eructations(詞匯)do nothing for the climate. Livestock are responsible for 14.5% of all anthropogenic(詞匯)greenhouse gases, according to the UN Food and Agriculture Organisation (FAO).飼養肉用動物已對世界環境產生了巨大的影響。二十世紀，農場動物(家禽家畜)數量劇增。目前全球有超過200億只雞、15億頭牛和10億只羊。飼養這些禽畜占用了世界上四分之一的土地，消耗了全世界30%的農作物。它們還大量消耗水資源——每生產一公斤牛肉大約需要1.5萬升水，而生產一公斤玉米或小麥只需1500升。這些動物的噯氣也對氣候毫無益處。聯合國糧農組織稱，牲畜造成了14.5%的人為溫室氣體。

How then may the planet be fed sustainably? One set of answers revolves around convincing people to put different things on their plates. Vegetarians have the simplest solution of all, but try telling people in sub-Saharan Africa that they should stick to(句型)cassava. Encouraging people to eat more fish rather than more meat is a better answer. Human consumption of fish has now overtaken that of beef, and aquaculture accounts for half of all the fish people eat. But almost 90% of wild stocks are fished either at or beyond their sustainable limits. And farmed fish, particularly salmon, are often fed on smaller fish that themselves are caught at sea. A fashionable idea is for Westerners to eat more insects, which contain up to three times as much protein as beef and already form an integral or supplementary part of up to 2bn people’s diets, according to the FAO. But for that to happen, many will have to get over the “yuck”(詞匯) factor. 那么，怎樣才能可持續地為人類提供食物?有一套應對方案圍繞著說服人們吃不同的食物展開。素食者的解決辦法最簡單，不過試試告訴撒哈拉以南非洲的人們應該只吃木薯會怎樣。更好的答案是鼓勵人們多吃魚而不是多吃肉。人類對魚類的消費量現在已超過牛肉，而這些魚有一半來自水產養殖。然而，近90%的野生魚類的捕撈量已達到或超過了可持續的限度。養殖魚類，特別是三文魚，經常被喂食從海里捕獲的小魚。一個時興的想法是讓西方人多吃昆蟲。昆蟲的蛋白質含量是牛肉的三倍(句型)，而且根據糧農組織的數據，昆蟲已經成為20億人飲食中不可或缺的部分或他們的補充食物。但要實現這一點，許多人將必須克服“惡心”的感覺。

Another set of answers involves using technology to create artificial protein. Investors such as Bill Gates and Richard Branson have backed artificial-meat startups that grow beef and poultry from animal cells. Tyson Foods, a meat processor, is an unlikely fan of plant-based proteins. Scientists are also looking at genetic modificationsto animals—to increase the muscle of cattle or to reduce infections among farmed fish. 另一系列答案涉及到運用技術來創造出人工蛋白質。比爾·蓋茨和理查德·布蘭森等投資者都資助了人造肉方面的創業公司，這些公司通過動物細胞培育牛肉和禽肉。出乎意料的(句型)是，肉類加工企業泰森食品公司也是植物性蛋白質的支持者。科學家們也在研究針對動物的基因改造技術，以提高牛的肌肉量或減少養殖魚類的感染。

Innovations such as these have enormous potential, if they can be industrialised and win over wary consumers. But changing what humans eat is not the only route to feeding a growing population more sustainably. Another, less obvious, approach is to alter what animals themselves eat. It is here that technology may have the biggest impact soonest. 如果這樣的創新能夠工業化并贏得謹慎的消費者的支持(句型)，它們就有巨大的潛力。但是，要以更可持續的方式養活日益增長的人口，改變人類的飲食并非唯一途徑。另一個不那么顯而易見的方法是改變動物的飼料。正是在這方面，技術可能會以最快的速度產生最大的影響。

One source of improvement lies in the more efficient use of crops to feed animals. The proliferation of mills that process grain into feed is helping in places such as sub-Saharan Africa, for example. Data-intensive farming is helping improve agricultural yields of feed crops like soyabeans by carefully monitoring the use of water and fertiliser. 一個改進的途徑是更高效地利用農作物來飼養動物。例如，在撒哈拉以南非洲等地，把谷物加工成飼料的工廠數量激增，對這些地區很有助益。通過仔細監測水和化肥的使用，數據密集型農業(詞匯)能幫助提高大豆等飼料作物的產量。

Eat shit and diet

A more radical approach is to change animals’ diets. Efforts to reduce the amount of fish meal used in aquaculture have already paid dividends(句型). In 1990 90% of salmon feed used in Norway was fish meal, but by 2013 greater use of plant matter had reduced that figure to 30%. More can be done. At most 20% of protein in grains fed to animals is converted to edible protein; the rest is turned into waste products. Cargill, an agricultural giant, broke ground this year on the world’s largest gas-fermentation facility, in partnership with Calysta, a Californian firm that makes feed out of natural gas. After feeding bacteria called methanotrophs with methane, they can be turned into protein pellets(詞匯)for fish and livestock. Insects are also an option. Flies and maggots can be raised on manure and organic waste, instead of grains, and then fed to cattle, chicken and fish.

奇特飼料

更激進的方法是改變動物的飼料。減少水產養殖中對魚粉的用量已經產生回報。1990年，挪威90%的三文魚飼料是魚粉，但到2013年，植物性飼料用量的提高使這一數字降至30%。還有更多辦法。在用來飼養動物的谷物中，最多只有20%的蛋白質轉化為可食用蛋白質，剩下的則變成廢物。農產品巨頭嘉吉今年破土開建世界最大的天然氣發酵工廠，合作伙伴是用天然氣生產飼料的加州企業Calysta。用甲烷喂養被稱為甲烷氧化菌(詞匯)的細菌，可將它們轉化為喂養魚和家畜的蛋白顆粒。昆蟲也是一個選擇。蒼蠅和蛆可以用糞便和有機廢物飼養而無需谷物，然后再把它們喂給牛、雞和魚。

The FAO has warned that by 2050 the planet will need to produce 70% more food than it did in 2009. The idea of chomping on more bugs and eating lab-grown meat may capture the imagination. But the path to food sustainability also runs through animals’ stomachs.糧農組織警告說，到2050年，地球將需要生產出比2009年多70%的食物。大口嚼蟲子和啃人造肉的想法可能會讓人浮想聯翩，但食物可持續性還需要靠(句型)改造動物的胃來實現。